7.62 vs .243

I've been in the market for another deer rifle, this time purely "mid-range". Now, I already own a .243, but I am picking up a Saiga 7.62 x39 in the next few days. Never mind accuracy, as I have both guns already (the first Saiga is purely tactical), and both can hit where I aim, but am I better off with a lighter, faster round in the .243, which I primarily coyote hunt with? Or, do I follow my gut and use the low and slow, heavier 7.62? I've killed game with both (varmints), deer with neither. Only experienced answers and opinions, not interested in consolation calibers. I don't care for 30-06, use .308 for primarily stand locations with 300+ yard shots, and 300 win mag for unknowns. These two will fill a niche, but only one is getting carried. Thanks fellas.

The 7.62 x 39 does not have near the muzzle energy or velocity that the .243 has. That being said, the 7.62x39 bleeds off quickly in velocity past 200m and the drop is better measured in feet than inches once past the 200 m mark.

There is a reason why the Russian 5.54 has been in use longer that the 7.62 x 39.

The 243 With a 95 or 100gr bullet shoots faster, flatter, farther, I would go with it. I have shot a lot of 7.62X39 and I like it but would feel short changed
hunting with it.
For me the 7.62x39 is a good 100-150 yard cartridge,but the 243 can handle
that and a hole lot more.
With the way my luck runs I would carry the 7.62x39 and the only buck I would see would be at 300-350 yards, what a bummer but with my 243 that would call for a smile and a giggle before the shot.

I have both, and often thought to use the 7.62 just for my woods stands. I have yet to shoot at a deer with it, but I think it would perform well to 200yrds.
My father and I got a deal on a thousand rounds of 7.62, and its about time to start shooting them up.